Resistor



Oct. 19, 1954 w. M. HICKS RESISTOR Filed Dec. l5, 1950 RNVENTQR fl/MMMM. H/c/gs.

ATTORNEYS:

Patented Oct. 19, 1954 UNITED STATES PATENT OFFICE RE'sIsToR William M.Hicks, Glen. Head, N. Y. Application December 15, 195o, serial No..200,889

8- Claims. l

This. invention relates to electrical resistances.

The manufacture of resistances has heretofore been unsatisfactorybecause of the complicated processes employed requiring both substantialtime and expense, and also dueto the failure of the resistance materialemployed as the result of' thermal shock received from the heat ofsoldering conductor ends to the resistor terminals.

It is an object of this invention to provide simple and efficientresistors.

Another object of the invention is to provide a method of manufacturingresistors whereby they may be made in multiple, in the form of a numberof separate units, or as units comprising a multiple number ofresistances, or both.

Another object of the invention is to provide a simplified process forthe manufacture of resistors whereby the speed and cost of manufacturemay both be reduced.

Another object of the invention is to provide a resistance material ofimproved quality.

Another object of the invention is to provide a resistor wherein twospaced electrical conductive areas are bridged by an area of controlledelectrical conductivity.

Other objects of the invention will be in part obvious or in partpointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, arrangements of parts, and in the severalsteps and relation and order of each of said steps to one or more of theothers thereof, all as will be pointed out in the following description,and the scope of the application of which will be indicated inthefollowing claims.

The invention will best be understood if. the following description isread in connection with the drawings, in which,

Figure 1 is a plan view of a rst sheet comprising a backing memberhaving thereon deposits of electrically conductive material;

Figure 2 is a plan view of a second sheet comprising a backing memberhaving thereon deposits of resistance material;

Figure 3 is an end view showing the sheet of Figure 2 inverted and beingsuperimposed upon the sheet of Figure l;

Figure 4 is a view similar to Figure 3 showing one sheet on the otherwith the deposits of resistance material bridging the pairs of spaceddeposits of conductive material;

Figure 5 is a plan View of a multiple resistor unit blocked out from theassembly shown in Figure 4;

Figure 6 is a plan view of another multiple resister unit blanked outfromv theV assembly shown in Figure 4 and` comprising the column ofdeposits shown in the middle of Figure l;

Figure 7 is a plan View of a single resistor unit blanked out from theassembly shown in Figure 4 and comprising the pair of deposits ofconductive material shown in the upper right hand corner of Figure 1 asviewed by the reader;

Figure 8 is a View in perspective of the resist,- ance unit shown inFigure 7, showing the asbestos, paper or other backing removed above thespaced conductive areas of the unit, and with a conductor end solderedto one of said areas;

Figure` 9 isa side elevationv of a backing sheet with a lamination ofmetal foil superimposed upon it;

Figure l0 is a side view showing the assembly of Figure 9 after portionsof metal foil have been removed;

Figure ll shows the assembly of Figure l0 with deposits of resistancecomposition bridging the spaces between pairs of deposits of conductivematerial;

Figure l2 is a perspective view of a resistance unit stamped from theassembly shown in Figure 1l, with a conductor end. soldered to one ofthe conductive areas of the unit;

Figure 13 is a side elevation of the resistance unit shown in Figure l2;and

Figure 14 is a side elevation ofV a longitudinal cross section throughthe resistor unit shown in Figure l2.

My method comprises broadly the steps of placing deposits ofelectrically conductive material, preferably deposits of metal, such forexample as copper or silver, on a backing member able to withstandtemperatures on the order of 350 F., in pairs of opposed, spaceddeposits. In Figure 1 the pairs of spaced deposits I2 are shown arrangedin a column and close together with the lateral margins of the depositsof one pair separated by only narrow portions of the `insulating memberI. Also on the surface of member Ill are shown the pairs of opposedspaced deposits I6 which are smaller than the deposits I2 but otherwisesimilarly disposed with respect to one another; and also on member Itare shown the two deposits i8 disposed in opposed spaced relation.

On backing member 20, which is also of insulating material able towithstand temperaturesy on the order of 350 F., are the deposits 22 ofresistance material. These deposits are of a size, and disposed onmember 20, so that when the surface of member 20 bearing the deposits 22is placed over and against the face of member I0 bearing the depositsI2, the deposits 22 will register with. and bridge, the spaces 24between the pairs of deposits I2. Similar deposits 26 of resistancematerial are shown on member 20, of a size, and in position to registerwith, and bridge, the spaces 28 between the pairs of deposits I6 onmember IU; and a single deposit of electrical resistance material 30 isshown on member I0 of a size and in a position to register with andbridge the space 32 between the deposits I8 on member I0.

After backing members I and 20 have been placed in face to face contact,with the resistance material deposits 22, 26 and 30 in register with,and bridging, the respective spaces 24, 28 and 32 on member I0, I preferto cure the assembly thus formed preferably at a temperature of about350 F., for a period of from thirty minutes to one hour. By this curingstep the resistance material I employ is softened and flows intointimate contact with the spaced electrical conductive deposits which itbridges, and when it rehardens, following the curing step, it adheresfirmly to said metal deposits thus providing a good contact and unionbetween the spaced conductive deposits and the bridging resistancematerial.

After the curing step I pierce and blank out from the assembly shown inFigure 4 multiple or single resistance units comprising pairs of spacedelectrically conductive areas and the bridging areas of resistancematerial, thus forming for example the multiple units shown in Figures 5and 6, and the single resistor shown in Figure 7.

It is incidental to this invention how the deposits of conductivematerial are placed on member I0 and how the deposits of resistancematerial are placed upon the member 20. For the purpose of thisinvention these deposits may be made in any suitable way. For examplethey may be painted or printed on the respective members I0 and 20. Ifdesired the whole surface of member I0 may be initially covered withconductive material and portions thereof thereafter removed in anysuitable way as for example by a photo-etching process.

And, if desired, the deposits of resistance composition may be placedupon the surface of member 20 through a silk screen, which process iswell known and need not be described here.

The members I0 and 20 which serve as backers for the deposits ofconductive material and resistance material respectively may be ofvarious compositions and of various thicknesses. Thus for example theymay be sheets or boards of asbestos, or sheets or boards comprised byglass fiber with a resin binder, the resin selected being one capable ofwithstanding temperatures on the order of 350 F.

In order to attach the conductive end areas of a completed resistor to aconductor, as by soldering, I remove a portion of one of the backingmembers, as illustrated in Figure 8, and solder the exposed core of aconductor member C to the exposed conductive area. I have found thatwhere asbestos paper is used as the backing it may be readily removedfrom over a portion of a conductive area by use of a wire brush.

It will also be understood that instead of making the deposits I2, I6and I8 of resistance material on a separate backing, such as 20, theymay be made directly on the backing I0, in any suitable way to iill thespaces 24, 28 and 32 respectively and somewhat overlap the said pairs ofopposed conductive areas and thus to bridge the said opposed pairs ofelectrically conductive areas.

When this method is employed one surface of the conductive areas, I2,I6, and I8 will be exposed and ready for a conductor C to be solderedthereto, as illustrated in Figure l2. As shown in Figures 9 and 10 thepairs of opposed deposits I2, IE and I8, are made by first superimposingon backing I0 a sheet II of metal foil and removing the sheet, as byphoto-etching, leaving only said areas I2, I6, and I8 and the like, toprovide pairs of spaced, opposed conductive deposits on backing I0.

It is, however, preferred to place the deposits 22, 26 and 30 initiallyon a second, separate backing member, such as 20. It will be observedthat when this is done, in the assembly, as shown in Figures 3 and 4,the deposits 22, 2B and 30 will complement, and somewhat overlap, thedeposits I2, I4 and I6, and form together with them a layer orlamination intermediate the members I0 and 20, and that the protectionthus afforded to the deposits by members I0 and 28 continues after theunits have been stamped out, and thus a finished product is provided inwhich both the electrically conductive material and resistance materialis well protected from injury caused for example by inadvertent blows,scratches, etc.

For said resistance material, illustrated by the deposits 22, 26 and 30,I prefer to employ a composition comprising powdered carbon, an inertller, such for example as sodium silicate, and a resin able to withstandtemperatures of 360 F., or more, such, for example, as ethoxyline resin.Ethoxyline resin is the condensation product of epichlorhydrin with abis-phenol (1950 Modern Plastics Encyclopedia and Engineers Handbook,page 785, rst column). This resin is described in an article entitledEthoxylines-a new group of triple-function resins, by Dr. EdwardPreiswerk and Dr. Conrad Meyerhans, Plastics Research Department, Ciba,Ltd., which appeared in Electrical Manufacturing, issue of July 1949. Ihave found that this composition satisfactorily withstands the thermalshock due to soldering the conductor ends to the resistor terminals,without breaking the bond between the electrically conductive materialand the resistance material. Carbon and resin in the form of dry powderis readily mixed with sodium silicate, in liquid phase in its originalstate, forming a composition which I have found easy to apply by thesilk screen method.

This mixture of ingredients gives a resistance composition of steady andcontrolled electrical conductivity. The ethoxyline resin forms a goodbond with the conductive material deposits and its backing during thecuring step, and, in combination with carbon and sodium silicate, formsa composition the conductivity of which does not vary substantially withtime under a given load.

I have had very satisfactory results using backing members I0 and 20comprising asbestos paper, and glass fiber coated with ethoxyline resin,respectively.

I have found that with a pair of metal deposits each approximatelyone-quarter inch in diameter and one-hundredth (.0l0") of an inch thick,and spaced apart approximately three-eighths of an inch, and a bridgingresistance composition comprising, by volume Per cent Carbon 33Ethoxyline resin 17 Sodium silicate 50 the total resistance obtained is2500 ohms, and, keeping the other factors the same and changing theresistance composition to the following, by volume Per cent Carbon 27Ethoxyline resin 25 Sodium silicate 50 the total resistance is increasedto 500,000 ohms.

In each case a good bond was obtained between the metal deposits and theresistance composition.

Resistors embodying my invention are durable and dependable in use, andcan be manufactured in large numbers simultaneously, in multiple orsingle units, speedily, and at low cost.

It Will thus be seen that there has been provided by this invention amethod and an article in which the various objects hereinabove set forthtogether with many thoroughly practical advantages are successfullyachieved. As various possible embodiments might be made of themechanical features of the above invention and as the art hereindescribed might be varied in various parts, all without departing fromthe scope of the invention, it is to be understood that all matterhereinbefore set forth or shown in the accompanying drawing is to beinterpreted as illustrative and not in a limiting sense.

What I claim is:

1. The method of forming resistors which comprises, orming deposits ofelectrically conductive material in spaced opposed pairs of deposits ona first backing member, forming on a second backing member deposits of acomposition of controlled conductivity in sizes to bridge the spacesbetween said pairs of deposits on said rst backing member, superimposingone of said backing members on the other with their deposit bearingfaces in opposition and with said deposits of controlled electricalconductivity in bridging relation to said pairs of deposits ofelectrically conductive material respectively, and blanizing out fromsaid superimposed sheets the areas having deposits thereon.

2. The method of making electrical resistances which comprises, formingdeposits of electrically conductive material in spaced opposed pairs ofdeposits on a first backing sheet able to withstand temperature on theorder of 350 F., forming, on a second backing sheet able to withstandtemperatures on the order of 350 F., deposits of a resistancecomposition in amounts suicient to bridge the spaces between said pairsof deposits Cil backing sheet able to withstand temperatures on theorder of 350 F., deposits of a resistance composition in amountssumcient to bridge the spaces between said pairs of deposits on saidfirst backing sheet, superimposing one of said sheets on the other inface to face relation thereby positioning the resistance compositiondeposits in bridging relation to said pairs of deposits of electricallyconductive material respectively, curing the superimposed sheets for aperiod of approximately thirty minutes to one hour at 350 F. to causesaid resistance composition to flow and adhere to said conductivematerial, and blanking out from said superimposed sheets the areashaving said deposits thereon.

4. The method claimed in claim l including the step of securing saidsheets together in superimposed position prior to the stampingoperation.

5. The method claimed in claim l including the step of treating theblanked out portions of said sheets to cause the opposed blanked outportions of said sheets to adhere together.

6. The article comprising a backing member adapted to withstandtemperatures on the order of 350 F. and having on its face a pluralityof electrically conductive areas, a second backing member adapted towithstand temperatures on the order of 350 F. having on its face an areaof electrically controlled conductivity, said backing members beingdisposed in face to face relation with the said deposit on said secondbacking member positioned in bridging relation to said deposits on saidfirst backing member.

'7. A resistor comprising an insulating base, having thereon a pluralityof deposits of electrically conductive material spaced apart on saidbase and bridged by a deposit of carbon, an inert ller, and ethoxylineresin obtained as the condensation product of epichlorhydrin lwith abisphenol.

8. A resistor comprising an insulating base, having thereon a pluralityof deposits of electrically conductive material spaced apart on saidbase and bridged by a deposit comprising carbon, an inert ller, andresin in the form of dry powder obtained as the condensation product ofepichlorhydrin with a bis-phenol.

References Cited in the ille of this patent UNITED STATES PATENTS NumberName Date 1,985,166 Haroldson Dec. 1B, 1934 2,005,922 Stoekle June 25,1935 2,206,780 Linton July 2, 1940 2,441,960 Eisler May 25, 19482,526,059 Zabel Oct. 17, 1950 OTHER REFERENCES Ethoxylines, a New Groupof Triple-Function Resins, Electrical Manufacturing, by Preiswerk etal., reprinted from Electrical Manufacturing of July 1949.

Brunnetti et al.: Printed Circuit Technique, Nov. l5, 1947, Bureau ofStandards Circular No. 468.

